Correlation between foveal microvasculature and inner retinal layer thickness in type 2 diabetes: an optical coherence tomography angiography study

Abstract

Aim The aim of this study was to evaluate the correlation between foveal microvasculature and inner retinal layer (IRL) thinning in patients with type 2 diabetes using optical coherence tomography angiography (OCTA).Patients and methods This is a prospective comparative study that included 100 eyes of 100 subjects: 50 eyes of diabetic patients with type 2 diabetes having mild to moderate nonproliferative diabetic retinopathy (NPDR) and 50 eyes of normal subjects. Foveal avascular zone (FAZ) area and vessel density of parafoveal and perifoveal areas were calculated using OCTA. The IRL thickness was measured using optical coherence tomography (OCT). The correlation between the IRL thickness and both FAZ area and macular vessel density was measured.Results The mean FAZ area was significantly larger in the NPDR group (0.69±0.01 mm2) than in the normal eyes group (0.45±0.02 mm2), (P=0.01). The mean parafoveal and perifoveal vessel density in the superficial capillary layer were significantly decreased in eyes with NPDR (46.7±6.5% and 43.8±7.1%, respectively) than in normal eyes (69.5±4.2% and 66.2±4.3%, respectively) (P=0.001). The mean parafoveal and perifoveal vessel density in the deep capillary layer had significantly lower values in eyes with NPDR (51.3±2.3% and 49.5±4.2%, respectively) than in normal eyes (70.1±5.4% and 68.3±3.73%, respectively), (P=0.001). The mean IRL thickness was significantly less in the NPDR eyes (54.7±6.8 μm) than in normal eyes (79.3±6.9 μm), (P=0.001). A statistically significant correlation was found between the IRL thickness and both FAZ area and macular vessel density in eyes with NPDR (P<0.001).Conclusion OCTA revealed that foveal microcirculatory alterations (FAZ area and macular vessel density) in diabetic eyes were related to the IRL thickness.